Quantitative studies of Purkinje cell population over Crus I & II near the midline showed significant atrophy of 3 individuals undergoing implantation of cerebellar stimulators & postmortem material from 4 other epileptics. Five normal autopsy specimens showed Purkinje populations nearly twice the epileptic. This finding brings into question the therapeutic rationale of cerebellar stimulation which is usually considered to be to increase the inhibitory discharge of the Purkinje cells. Using a radioenzymatic assay method the norepinephrine content of the CSF was found to decrease following stimulation of the striatum in 5 patients undergoing stereotaxic thalamotomy. Control studies ruled out effects of simple surgical intervention. This suggested stimulation induced inhibition of noradrenergic pathways. In patients with temporal lobe seizures subject to additional foci. In this complicated group, most cases would not have been accepted for temporal lobectomy without the use of depth electrodes. The additional information permitted the cure or significant improvement in some 25-50% of the patients with a follow-up averaging 8.2 years.